Provide a C language wrapper function for io_channel_read_blk64() and
io_channel_write_blk64() instead of using a C preprocessor macro, with
an fallback to the old 32-bit functions if an application-provided I/O
channel manager doesn't supply 64-bit method functions and the block
numbers can fit in 32-bit integer.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Jose R. Santos